Electric smelting furnace with bottom tapping hole



N. E. BUGGE ELECTRIC SMELTING FURNACE WITH BOTTOM TAPPINGHOLE Filed July5l, 1958 BYMJMMQ LAAG ATTORNEYS.

Oct. 25, 1960 N.. E. BUGGE 2,957,936

ELECTRIC SMELTING FURNACE. WITH BOTTOM TAPPING HOLE Filed July 31, 19583 Sheets-Sheet 2 N km O O N- gi O 1L N f Q 4 x w INVENTOR. NILS EMILBUGGE BY Xu kamhw A TTORNE YS.

Oct. 25, 1960 N. E. BUGGE 2,957,936

ELECTRIC SMELTING FURNACE WITH BOTTOM TAPPING HOLE .//F'iled July 5l,1958 3 Sheets-Sheet 3 Unite ELECTRIC SMELTING FURNACE WITH BO'I'IOMTAPPING HOLE Nils Emil Bugge, Oslo, Norway, assignor to Elektrokemisk A/S, Oslo, Norway, a corporation of Norway This invention relates toelectric smelting furnaces particularly of the type in which anelectrode penetrates deep down into a charge to be smelted, and has todo both with the construction of the furnaces themselves and with theiroperation.

Furnaces of this type are invariably tapped through one or more tapholes arranged in a generally horizontal direction running through thefurnace wall on the same level as the inside furnace bottom.

The molten material produced in the furnace is tapped into castingmachinery or ladles, cars or the like placed outside the furnace. Insome cases furnaces of this type are made to rotate (see for exampleEllefsen Patent No. 2,300,355) and in such case, where the tap holesmove slowly around, cars moving on circular rails around the furnaceoften are used so that the charge from the furnace may be caused to flowinto the tapping cars independent of the position of the tap holes.

The number of tap holes in any given furnace depends on the furnace typeas well as the type and quality of the material produced. For examplestationary furnaces usually have from 1 to 3 tap holes whereas rotatingfurnaces have as many as nine tap holes.

In any case it is essential that the tap holes are accessible with thenecessary tapping equipment which includes not only the cars or vesselsfor receiving the product but also the devices for opening and closingthe holes. Further it is important to provide space enough for the crewoperating this equipment in those areas where the tapping holes may belocated. This demands considerable space which may be valuable in aplant.

During the tapping of the furnaces from the usual tap holes the materialflows from the high temperature zones of the inner part of the furnaceout to the tapping hole in the furnace side wall where the temperatureordinarily is much lower. The resulting cooling of the product may causedifficulty during the tapping as the product may solidify, therebyplugging up the tap holes. In some cases, as for example, in theproduction of corundum, this cooling problem is so acute that tapping isvirtually impossible and such materials have to be produced by blocksmelting.

The cooling down of the charge and the change in its fluidity may besaid to be a function of the distance from the high temperature zone(the smelting zone) to the tapping hole and every change of thisdistance is of great importance especially for calcium carbide and otherhigh temperature products.

It is further recognized that the effective area of the high temperaturezone may vary with the furnace load and this again will create avariable condition in tapping.

In the case of rotating furnaces another factor which will vary thedistance from the smelting zone to the tapping hole is the fact that theelectrodes are usually arranged in the form of a triangle and remainstationary whereas the tapping holes formed in the rotating part of thefurnace will move relative to the electrodes and thus the distance froma given tap hole to an electrode will be rates Patent O continuouslyvarying. It has been found that this variation in distance in rotatingfurnaces is sufficient to change the rate of ow of material such ascarbide and also as a new tapping hole may come into position some timeis consumed before it is hot enough for the charge to flow properly.These variations cause intermittent and pulsating production and thishas to be taken into consideration in designing the installation.

Another drawback connected with the ordinary tapping hole in rotatingfurnaces is that the frequent opening and closing of the tap holes (evenwith continuous tapping) causes wear of the refractory lining around theholes and the ow of the material into the tapping holes may causecorrodng or wear on the inside furnace lining.

In some instances the factors of wear and damage on the tap hole may begreat enough so that it has been found necessary to place the tap holesrelatively far from the high temperature zone and this again createsdiculties as have already been pointed out.

The present invention aims to overcome these difficulties by soconstructing the furnace and by providing special mechanism so that thefurnace can be tapped from the bottom of the pot in an area near thecenter of the furnace. In such case the heat developed underneath thefurnace will be very great so that it is virtually impossible forworkmen to stay there to control the tapping and it is necessary toprovide special equipment for opening the furnace tap and closing itagain and for handling the charge as it comes from the furnace.

This invention can readily be understood from the illustrative exampleshown in the accompanying drawings in which:

Fig. 1 is a cross section through a furnace embodying my invention.

Fig, 2 is a plan View on line 2-2 of Fig. 1.

Fig. 3 is a view similar to Fig. 2 with the parts in different position;and

Fig. 4 shows certain permissible modications.

In these drawings the actual furnace pot is indicated by Ithe numeral 10and this pot is carried on circular eye-beams 12 and radial supportingbeams 14. The radial eye-beams 14 do not run all the way to the centerbut connect with circular eye-beams 16 and at their ends carry acircular shield 18. This shield should be either-of heat resistantmaterial or be uid cooled as Idescribed later in connection with Fig. 4.This shield not only protects the metal sup-port beams from the heat of`the molten material during tapping, but it also Vserves to maintain acushion of hot reducing gases around the tap-hole. This will prevent thecharge from being chilled as it first leaves the furnace and reducesoxidation of the material around the tap-hole.

In this example the pot is constructed so that it will rotate and ismounted on wheels 20 which run on a crcular track 22. The electrodes forsmelting the charge are indicated at 24. The furnace is caused to rotateby a motor 26 which drives a shaft 28 and gearing 30.

At approximately the center of rotation the pot 10 is provided with atap-hole 32 and preferably at the bottom of the tap-hole there is formeda removable block 34 of ceramic material which is held in place by bars36 which pass through the circular eye-beam 16 and the shield 18. Thisblock is provided so that it can be readily replaced in the event ofwear.

When the furnace is discharging the molten material ows into a movablechute and may be discharged into any kind of receptacle such as, forexample, the endless transport conveyor 40. The chute 3S can be movedout from under the tap-hole by means of the cylinder 42 which is fluidoperated preferably by air supplied by the pipes 44. It may be notedthat the air supplied by the pipes 44 is controlled by a valve 45located at the side of the pot so that the movement of the chute 38 canbe controlled from that point. Preferably a tapping ladle 46 is providedbelow the chute to catch any of the molten product or slag that may notbe caught by the chute 3S.

To control the tapping `and blocking of the tap hole a mechanism issupplied carried on the fixed shaft 48 adjacent the periphery of theunder part of the pot. A bar 50 rotates on this shaft which extends toan operating handle 52. The inner end of this bar :is supported by aninclined support member 54. Carried by the inner end of the bar 50 is acylinder 56 controlling the movement of a piston 58. By moving thehandle 52 the piston 58 can be swung directly beneath the tap-hole 32 asshown in Fig. 3 or it may be swung out towards the edge of the furnacewhere it is accessible to the workmen as indicated in Fig. 2. The upperend lof the piston 58 is made pointed and is provided with a removableplate 60. When it is desired to block the furnace the handle 52 is swungaround and the plate 60 is put on the piston 58 and the blockingcompound indicated at 62 is put on the plate 60. The piston is thenforced upward by fluid pressure admitted through the lower of the pipes64 which may, for example, be supplied with compressed air through thepipe 66. A flexible connection is supplied as indicated at 68 to permitthe pipes to be rotated with the cylinder 56. This will force theblocking cornpound 62 into the bottom of the tap-hole 32 to close thetap-hole.

When it is desired to open the tap-hole the handle 52 is swung around sothat access can be had to the pis-ton 58. The plate 60 is then removedand when the piston 58 is forced upward it will pierce the tappingcompound and open the tap-hole 32. To assist the action of the piston 58it preferably is connected into the electrical circuit so that it willserve as a ltapping electrode. For this purpose I supply a flexibleconnection 7G connected to a bus bar 72 controlled by ya switch notshown. Current is allowed lto flow through the connection 70 and piston58 when it is desired to use the piston 58 for opening the tap-hole. Agraphite block indicated at 74 is preferably supplied to protect thecylinder 56 and pipe 64 from any hot metal that may drop out of thetap-hole during the blocking or unblocking operations. If desired anyconvenient means may be employed to cause ya current of cool -air toflow under the pot to prevent undue heat from developing.

Obviously during the time that the tap-hole is being either blocked oropened the movable chute 38 is drawn of to oneY side so that the piston58 can function `as has been described.

In operating a furnace such as has been described ordinarily one of twomethods of operation will be employed. In one case the tap-hole is madesmall enough so that in ordinary operation continuous tapping takesplace and the tapping `and blocking mechanism is only used under specialoccasions. In the other case when the furnace is tapped, it will beallowed to drain until virtually all of the desired product and slag hasbeen discharged and then it will be reblocked and a new charge smeltedin the furnace.

In Fig. 4 I show some permissible alternatives. In this case the bottomof the furnace 11 is slanted toward the center and a central well 13 isformed in the bottom of the pot. Obviously with this arrangement, asmetal is smelted from the ore and becomes fluid, it will flow toward thecenter of the furnace pot and be collected in the well 13, thus having acontinuous supply of liquid material available for tapping. This is ofparticular importance when continuous tapping is used. In place of theremovable block 34 I supply a mouthpiece 35 which may be fluid cooledas, for example, with a silicone oil or other cooling media. Water maybe employed but ordinarily water is considered dangerous in connectionwith the heated parts of a furnace. Here also :the shield 19 is cooledwith the same type of fluid used in the mouthpiece 35. In this caseinstead of a blocking and unblocking mechanism a fluid cooled block 63is supplied oarried on a shaft 59 which will be operated by a cylindersimilar to the cylinder 56 and which may be rotated `out from under thetapping hole in the same way las the cylinder 56 `is rotated.

I-t is understood that the example given is intended only by way ofillustration and that the same may be modified in any particular withoutdeparting from the spirit of my invention.

What I claim is:

1. An electric smelting furnace for electrothermic reduction of thecharge which includes ya pot having an outer metal shell that supports alining of refractory material therein, electrodes positioned within saidpot, means for supporting the pot so that access may be had to theunderside thereof, a tap hole running down through the bottom of the potthe mouth of which terminates adjacent the said outer metal shell, anannular flange the walls of which are held in substantially verticalposition against the bottom of the said pot to surround the mouth of thetap hole, said flange being spaced ia substantial distance away from themouth of the tap hole to project down below the level thereof wherebywhen the furnace is tapped a cushion of hot reducing gases will collectwithin the rannular flange to surround the mouth of the tap hole.

2. A structure as specified in claim 1 in which the furnace pot isadapted to rotate on its support means, a chute member underneath thepot adapted to receive molten material discharged -through said tap holeand means for conducting such mol-ten material out from under the po-tsaid means for conducting the molten m-aterial out from under the potbeing adapted to withdraw such molten material substantiallycontinuously so that lthe furnace may be operated with continuoustapping while the furnace is rotated.

3. A structure as specified in claim l, which further includes mechanismwhereby said chu-te may be moved horizontally out from under thetap-hole and means whereby such mechanism may be operated from aposition yat the side of the pot.

4. A structure as specified in claim 1, which further includes means forclosing the tap hole by inserting a plug into the tap hole vand meansoperable from the side of the pot whereby the tap-hole may be opened.

5. A structure as specified in claim 1, in which the bottom of the potis formed with a centrally located well out of which the tap-hole runsand in which the bottom part of the tap-hole is formed in the shape ofan inverted funnel and which further includes a member adapted to fitinto said inverted funnel to close the tap hole.

6. A structure as specified in claim 4 in which the mechanism foropening the tap-hole may also be used for replugging the tap-hole.

References Cited in the ille of this patent UNITED STATES PATENTS Re.22,479 Dobscha May 16, 1944 284,005 I-Iainsworth Aug. 28, 1883 343,954Follett lune 15, 1886 977,271 Callaghan Nov. 29, 1910 1,286,632 HodgeDec. 3, 1918 1,360,520 Gray Nov. 30, 1920 2,045,073 Eldridge June 23,1936 2,085,450 Rohn .inne 29, 1937 l i l L

